High voltage rectifier tube



J1me 1962 Q M. E. LOUGH ETAL 3,041,494

I HIGH VOLTAGE RECTIFIER TUBE Filed March 25, 1959 INVENTORS MERLIN E. Lamar: DEAN L. CURRY mmw Imam i) United States Patent a 3,041,494 HIGH VOLTAGE RECTIFIER TUBE Merlin E. Lough, Middletown, and Dean L. Curry,

Berkeley Heights, N.J., assignors to Radio Corporation of America, a corporation of Delaware Filed Mar. 25, 1959, Ser. No. 801,846 4 Claims. (Cl. 313-285) This invention relates to improvements in high voltage rectifiers, regulators and other electron tubes of the kind employing a tubular anode containing one or more metal targets which expand when subjected to heat generated as an incident to the impact of electrons thereon.

In tubes of the subject variety the enclosed metal target or targets may operate red hot, i.e., at a temperature of more than 1000 C. The thermal force of expansion (and contraction) thus present in the metal target may, and frequently does, buckle or otherwise distort its tubular support, thus throwing the target out of alignment with its cathode or cathode-grid assembly and eifective 1y ruining the tube Accordingly, the principal object of the present invention is to provide a method of and means for curing the above described and other less apparent objections to the target-supporting contrivances employed in present day electron tubes of the subject variety.

Another and specific object of the invention is to provide an improved anode-assembly of the cylindrical kind that contains and intercepts the beam-electrons, and one characterized by its enhanced ability to dissipate the resultant heat and X-ray radiations without mechanic-ally distorting said assembly or disturbing its alignment with respect to the source or the path of the beam electrons.

The foregoing and related objects are achieved in accordance with invention by the provision of an anode assembly comprising an electron conduit which incorpo rates a pedestal or supporting surface upon which the target for the electrons rests, with a minimum of clamping force, so that it is substantially free to expand and contract and indeed to slide a limited distance. When, as is usually the case, the conduit through which the electrons pass is circular in cross-section, the target or targets are preferably made square, whereby if the metal should be subjected to any force sufl'icient to bend it, the bend or bends can, predictably, be confined to its corners.

The invention is described in greater detail in connection with the accompanying single sheet of drawings,

7 v wherein:

FIG. 1 is a view in perspective of an electron tube with its envelope partly broken away to reveal a cylindrical flanged anode containing a target mounted in accordance with the principle of the invention;

FIG. 2 is an exploded view of the flanged anode of FIG. 1, showing the target disposed, without any clamping force, on the lower flange;

FIG. 3 is an elevational view of the device of FIG. 2 with its parts assembled and the walls of the device cutaway adjacent to its flanges to show the manner in which the target electrode is supported thereon; and

FIG. 4 is a sectional view of the target and its support, taken on the line 4-4 of FIG. 3.

In the drawings the invention is shown embodied in a high voltage regulator tube (e.g., type 6BK4 or type 6BD4A) comprising a glass envelope 1 containing a vertically arranged tripart, hollow cylindrical anode 3 having the open end of its distal part 3a presented across an intervening space s to a source of beam-electrons, and its proximal part 3c hermetically sealed to the glass and extending therethrough to provide an external electrical terminal 3t for the anode. The upper end of the distal section 3a and the lower end of the intermediate section 3b of the anode cylinder 3 terminate in a pair of ment (with the cathode) such as might be caused if the force of expansion (or contraction) in the target wereto be transmitted to the flanges 7 and 9, or through said flanges to any of the cylindrical parts of the anode 3.

When, as shown more clearly in FIGS. 2, 3 and4, the

target 11 is mounted in accordance with the principle of the invention, it is held on and against the surface 7s of the lower flange 7 principally by the force of gravity,

and without fixed connection with either the lowerflange:

7- or the upper flange 9 so'that it is substantially free to expand isotropically when it is subjected to heat generated as an incident to the impact of electrons thereon; To this end, referring now particularly to FIGS. 2 and 4,- the target, which may be made of tantalum, molybdenum. or other metal (or alloy) of very high melting point; takes the form of a noncircular, preferably square, plate,

11 of a dimension greater than the internal diameter 11 (FIG. 4) of the cylinder 3a yet so much smaller than the flange 7, upon which it rests, that there is a space between the edges of the target and the outer edge of said flange large enough to accommodate the circle of welds w (FIG. 4) which eventually join the two flanges 7 and 9 and limit the extent of any movement of the target thereon.

In one practical embodiment of the invention wherein the inner diameter of the type 302 stainless steel cylinder 3 was .500 inch and the outer diameter of its flanges 7 and 9 was .750 inch the target plate 11, which was made of tantalum or molybdenum .005"007" thick was .525 inch square. Thus, in the absence of any restraining force the target 11 could move a limited distance on the flange 7 'without letting electrons by-pass the target area, and the metal of which the target was comprised was free to expand isotropically when it was subjected to heat (more than 1000 C.) generated as an incident to the impact of electrons thereon.

While the invention is not necessarily to be limited to any particular shape of target-plate, or to any specific pattern of welds, pins, or other means, for limiting the extent of the movement of said plate, it has nevertheless been found that a square target plate surrounded by a circular pattern of welds possesses certain advantages over other target shapes and other target-retaining means. The advantages of a square target flow from the fact that only its corners need be presented to the (inner) facing surfaces of the flanges 7 and 9. As a consequence, but little heat is transferred to the flanges by conduction. Furthermore, should one or more of the corners of a square target plate become wedged between the welds w and become subject to sufficient force (of expansion) to bend the plate, the bend or bends are confined to its corner areas and do not distort its central target area. Nor in no case has such wedging and/ or bending of the corners of target plate 11 caused the welds w to give way or the flanges to separate. By design there should be no clamping force exerted upon the square anode target 11 when the flanges 7 and 0 are joined by the welds w. However, variations in tolerances of the flanges or in the exact position of the welds can result in a slight clamping force being exerted. This is eliminated, however, once the assembly reaches its operating temperature.

In conclusion, attention is called to the fact that tubes constructed in accordance with the principle of the invention can be operated either in the vertical or horizontal position. When the tube is in the vertical position, the target 11 lies of its weight upon the horizontal lower flange 7, and when the tube is disposed horizontal- Patented June 26, 1962 f a metal target for electrons derived from said source, a

surface upon which said target rests, said target being held on and against said surface by the force of gravity and without fixed connection to said surface, whereby the metal of which said target is comprised is substantially free to expand isotropically when it is subjected to heat generated as an incident to the impact of'said electrons thereon.

2. The invention as set forth in claim 1 and wherein said electron target comprises a substantially square metal plate and is supported only. adjacent to its corners upon said surface.

3. An electron tube comprising an evacuated envelope containing a source of electrons, a hollow metal cylinder having an open distal end presented to said source, a proximal end portion hermetically sealed to said envelope and an intermediate portion including a pair of oppositely located outwardly extending flanges, and a metal plate disposed between said flanges with the central region of said plate extending across the bore of said cylinder and comprising a target for said electrons, said metal plate being loosely supported between said flanges to permit the metal of which said plate is comprised to expand and to contract when subjected to changes in temperature.

4. An electron discharge device having cathode means for directing an electron beam along a path, an elongated anode electrode positioned in said path for receiving said electron beam, said anode electrode including a pair of tubular members each having, at one end, an outwardly extending flange, said flanges being secured together adjacent to their peripheries, a sheet metal target member having edge portions received between said flanges to be supported thereby, said portions having relative movement with'respect to said flanges whereby stresses induced in said target member by electron bombardment are not References Cited in the file of this patent UNITED STATES PATENTS Karabats Apr. 28, 1959 

